The invention relates to a turbine blade assembly, in particular for a gas turbine and a method for assembling a turbine blade assembly.
Seal strips are used between adjacent turbine blades to prevent the ingress of hot gasses into a root cavity which can cause undesired heating of the disc rim and loss of efficiency. Where blades are assembled into the disc as a full ring (for interlocked designs or where differential platform/root and shroud skew angles are in evidence) seal strips cannot be introduced using the conventional sequential build methodology. More so a method must be devised to permit assembly and retention of the strips with the bladed disc complete.
Generally assemblies have been built up using sequential build techniques where single blades and strips are assembled to complete the full ring. Where blades are fitted as full sets then full length platform seal strips have not been utilised. In previous cases small seal plates have been fitted in upstream seal slots and retained using locking strips. This does not provide adequate coverage across the platform length in addition that seal strips are not used in high pressure turbine disc assemblies as locking plates are required for both blade retention and to prevent cross leakage of cooling air. This state of the art does not provide an adequate measure for preventing ingress of hot gas into the root cavities of the turbine blades.
EP 1 600 606 A1 discloses an arrangement of turbine blades with gaps between the platforms of adjacent turbine blades. These gaps are closed by sealing and damping elements in the form of strips. The sealing and damping strips are held in place by centrifugal forces.
Document U.S. Pat. No. 4,265,594 discloses a turbine blade arrangement with turbine blades having platforms with segments and cover plates extending in the longitudinal direction of the rotor axis. The gaps between the cover plates are provided with slots in which sealing strips are inserted.
Sealing arrangements for turbine vanes are described in GB 2 280 935 A, GB 1 580 884, WO 2004/074640 A1, GB 2 303 888 A, GB 2 182 399 A and JP 10184310 A.